Recently, the Tianzhou-7 cargo spacecraft flew into space, delivering new supplies to the Shenzhou-17 astronauts busy aboard China's space station.

Higher efficiency, heavier cargo... Since the space station entered the application and development phase, there have been many new changes in delivering goods to space.

　　Increased payload capacity

The Tianzhou-7 cargo spacecraft is the cargo spacecraft with the largest cargo transport capacity, the highest cargo transport efficiency, and the most comprehensive in-orbit support capability in service in the world today. As the first launch mission of China's manned space engineering program this year, Tianzhou-7 will deliver supplies to the two crews aboard the in-orbit Shenzhou-17 and the subsequent Shenzhou-18.

Previously, the launch of Tianzhou spacecraft often followed the principle of "provisions go ahead before the troops arrive," that is, before each flight crew set out, a cargo spacecraft was launched first to prepare supplies for the astronaut crew about to depart. Tianzhou-7, however, carries supplies for two crews, and the spacecraft's launch frequency has been adjusted to three launches every two years.

The reduction in launch frequency is attributable to the increased payload capacity of the Tianzhou cargo spacecraft. Starting with Tianzhou-6, the Tianzhou series spacecraft were "upgraded" to improved cargo spacecraft, with increases in both loading space and loading weight. Tianzhou-7 carries as many as more than 260 items of cargo for the astronaut system, space station system, application mission field, cargo spacecraft system, and engineering overall, with a total transported supply weight of about 5.6 tons, and is characterized by a wide variety of cargo types and many large items. Among them, large items such as customized cargo packages for test payloads carried by Tianzhou-7 each weigh more than 100 kilograms and will be used for in-orbit operation of the space station, in-orbit space science experiments, and life support for astronauts.

Living supplies for the astronaut crew are indispensable. For this mission, Tianzhou-7 has prepared 2,400 kilograms of living supplies for the astronaut crew, including special purchases for the Spring Festival of the Year of the Dragon and gift packages of fresh fruits and vegetables, among which fresh fruit accounts for nearly 90 kilograms. The Shenzhou-17 crew will spend the Spring Festival of the Year of the Dragon in space, and Tianzhou-7 has brought them "blind boxes" for the Year of the Dragon.

According to reports, China's space station has abundant supplies, which can not only support normal astronaut residency, platform maintenance and upgrades, and the conduct of large-scale in-orbit experimental missions, but can also additionally support astronaut residency for 3 months in emergencies.

　　Precise replenishment

At present, China's manned space engineering program has established a space-ground linked supply information system and developed models for the design life and design use of supplies, achieving precise replenishment and improving efficiency. Experts say that as in-orbit data from the construction phase accumulates, the models will become increasingly accurate and can precisely estimate future needs, achieving "replenish whatever is lacking," carrying neither too little nor too much, with supply efficiency continuously improving.

In addition, the Tianzhou-7 cargo spacecraft adopted a 3-hour fast rendezvous and docking plan for the first time. Compared with the conventional 6.5-hour fast rendezvous and docking plan, it further compresses the docking time, provides a more efficient way to transport supplies to the space station, and reduces the pressure on various systems during mission execution. At the same time, the use of this plan improves the cargo spacecraft's autonomous rendezvous and docking capability and further advances the development of rendezvous and docking technology.

In this delivery mission, Tianzhou-7 also carried a "new member" — a new-type power socket that allows independent in-orbit replacement of fuses. The power socket measures only 10 centimeters square, and despite its petite size, it features multiple in-orbit maintenance functions such as quick disassembly and assembly, slot alignment, and non-loosening locking, and will play a pivotal role in astronauts' in-orbit use of electricity on the space station.

In the early stage of space station construction, once a fuse in a power socket blew, the only option was to replace the entire unit, with astronauts bringing the power socket back to Earth for factory repair, which involved high repair costs and long cycles. As space science experiments within the space station gradually increased, more and more types of payloads were connected to power sockets, and power usage conditions and operating conditions became more complex, increasing the probability of abnormal fuse blowing inside power sockets; the whole-unit factory repair method no longer suited the new needs of manned spaceflight.

To this end, the development team of the Fifth Academy of the China Aerospace Science and Technology Corporation conducted research on fuse component maintenance technology based on the microgravity environment, optimizing the power socket maintenance method from "whole-unit repair" to "external component" repair. With the new-generation power socket, when performing in-orbit maintenance, astronauts only need to remove the external fuse component of the power socket and replace it with a new component, just like "tightening a screw," to complete the repair, which can greatly save costs and shorten repair cycles.

　　More scientific payloads

After entering routine operations, space science experiments account for an increasing proportion of astronauts' work. At present, there are 25 experiment and test racks in China's space station, and new experiment modules, equipment, and other items are constantly being rotated in.

It is understood that the space application system has a total of 61 uplink products in the Tianzhou-7 mission, including 16 standard cargo packages, 1 set of cell uplink life support device, and 1 set of 4°C uplink microfluidic chip, among others. After these application supplies are sent up, they will be transferred to the experimental facilities in the space station to carry out a total of 33 scientific experiments (tests) in space life science, space materials science, microgravity fluid physics and combustion science, involving 10 research institutes and 8 universities. After these application supplies are delivered to the space station, the in-orbit astronauts will install them into the corresponding experimental devices to carry out experiments; some experimental results can be transmitted back to the ground in real time, and some experimental samples will be brought back to the ground by the astronauts for further research. In addition, Tianzhou-7 also carried multiple scientific payloads, which are of great significance to subsequent space science research.

In this Tianzhou-7 mission, a scientific experiment jointly designed by researchers from Tsinghua University, the Institute of Microbiology of the Chinese Academy of Sciences, the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, and Dalian Maritime University will send a type of anaerobic archaea called methanogens to China's space station to verify whether they can survive in a simulated Mars environment and under the extreme conditions of cosmic radiation, helping humanity explore the major mystery of whether extraterrestrial life exists.